Cobalt-base alloy with high heat resistance and high strength and process for producing the same

a technology of cobalt-base alloy and high heat resistance, which is applied in the field of cobase alloy, can solve the problems of low stability of 3/sub>ta at high temperature, low strength of ni-base alloy, and low operating temperature, and achieve high alloy strengthening and good compatibility with the matrix

Active Publication Date: 2008-08-07
JAPAN SCI & TECH CORP
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  • Summary
  • Abstract
  • Description
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AI Technical Summary

Benefits of technology

[0004]The present inventors investigated and examined various precipitates which are effective in strengthening the Co-base alloy. As a result, the present inventor discovered a ternary compound Co3(Al,W) having the L12 structure and found that the ternary compound was an effective factor in strengthening the cobalt-base alloy. The Co3 (Al,W) has the same crystal structure as a Ni3Al (γ′) phase, which is a major strengthening phase of the Ni-base alloy and has a good compatibility with the matrix. Further, it contributes to the high strengthening of the alloy since it can be precipitated uniformly and finely.
[0005]An objective of the present invention is to provide a Co-base alloy with heat resistance equal to that of the conventional Ni-base alloys and an excellent textural stability which is obtained by precipitating and dispersing the Co3 (Al,W) having a high melting point to highly strengthen on the basis of the findings.

Problems solved by technology

However, Co3Ti has a low melting point and Co3Ta has a low stability at high temperature.
Thus, in the case of using materials made with Co3Ti and Co3Ta as strengthening phases, the upper limit of the operating temperature is only about 750° C. even when alloy elements are added.
A process including steps of: adding Ni, Al, and Ti etc., precipitating, and strengthening with the γ′ phase [Ni3(Al,Ti)] has been reported in Japanese Patent Application Laid-Open (JP-A) No. 59-129746, however, a significant strengthening equal to that of the Ni-base alloy has not been obtained.
However, it has not yet been put to practical use.

Method used

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  • Cobalt-base alloy with high heat resistance and high strength and process for producing the same
  • Cobalt-base alloy with high heat resistance and high strength and process for producing the same
  • Cobalt-base alloy with high heat resistance and high strength and process for producing the same

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0046]The Co-base alloy with the composition of Table 1 was smelted by high-frequency-induction dissolution in an inert gas atmosphere. The resulting product was casted to form an ingot, and then hot-rolled to a plate thickness of 3 mm at 1200° C. The test pieces obtained from the ingot and the hot-rolled plate were subjected to the solution treatment and aging treatment shown in Table 2, followed by texture observation, composition analysis, and characteristic test.

[0047]Each of the test results is shown in Table 3. In the Table, γ′ / D019 shows that precipitates are two types of γ′ phase and D019(Co3W) phase, D019 / μ shows that precipitates are two types of D019 phase and μ phase, and B2 / μ shows that precipitates are two types of B2 (CoAl) phase and μ phase.

[0048]In the samples of Test Nos. 1 to 13, one type of the γ′ phase was observed as a precipitate. As is apparent from the case of Test Nos. 1 and 2, it is found that a mechanical property such as hardness can be controlled by cha...

example 2

[0056]Table 4 shows alloy designs in which alloy components of Group (I) were added to Co—W—Al alloy. The amounts of Al and W were determined based on Alloy No. 3 of Table 1. The cobalt-base alloy adjusted to a predetermined composition was dissolved, casted, and hot-rolled in the same manner as described in Example 1, followed by heat-treating. The characteristics of the obtained hot-rolled plates are shown in Table 5.

TABLE 4Smelted cobalt-base alloy (Co; impurities removed fromthe remainder)Alloy component and content(% by mass)Alloy No.AlWBCYLa143.725.00.2 ———153.725.0—0.7 ——163.725.0——0.4—173.725.0———0.4183.725.00.030.03——

[0057]Since all components other than C were added trace elements in Group (I), a major change in the texture other than the addition of C was not observed. When a carbide is precipitated by addition of C, the Co-base alloy becomes hard. Both C and B tend to be segregated in the grain boundary segregation and they contribute to the improvement in high temperatu...

example 3

[0058]Table 6 shows alloy designs in which alloy components of Group (II) were added to Co—W—Al alloy. The Co-base alloy adjusted to a predetermined composition was dissolved, casted, and hot-rolled in the same manner as described in Example 1, followed by heat-treating. The characteristics of the obtained hot-rolled plates are shown in Table 7. For comparison, physical properties of Ni-base super alloy Waspaloy (Cr: 19.5%, Mo: 4.3%, Co: 13.5%, Al: 1.4%, Ti: 3%, C: 0.07%) are shown in Table 7 as Alloy No. 33.

TABLE 6Smelted cobalt-base alloy (Co; impurities removed fromthe remainder)Alloy component and content(% by mass)Alloy No.AlWAlloy component of Group (II)194.026.9Ni: 4.3203.425.4Ir: 5.4213.526.4Fe: 1.6223.526.4Cr: 1.5233.426.1Mo: 2.8243.425.4Re: 5.3253.526.4Ti: 1.4263.426.1Zr: 2.6273.425.5Hf: 5.0283.526.4V: 1.5293.426.1Nb: 2.7303.425.4Ta: 5.1313.623.9Cr: 3.7, Ta: 5.2323.826.0Ni: 16.6, Ta: 5.1

TABLE 7Alloy components, metal compositions in accordance with heat treatment condition...

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Abstract

A Co-base alloy which has a basic composition including, in terms of mass proportion, 0.1%-10% Al, 3.0-45% W, and Co as the remainder and has an intermetallic compound of the Ll2 type [Co3(Al,W)] dispersed and precipitated therein. Part of the Co may be replaced with Ni, Ir, Fe, Cr, Re, or Ru, while part of the Al and W may be replaced with Ni, Ti, Nb, Zr, V, Ta or Hf. The intermetallic compound [Co3(Al, W)] has a high melting point, and this compound and the matrix are mismatched little with respect to lattice constant. Thus, the cobalt-base alloy can have high-temperature strength equal to that of nickel-base alloys and excellent structure stability.

Description

TECHNICAL FIELD[0001]The present invention relates to a Co-base alloy suitable for applications where a high temperature strength is required or applications where a high strength and a high elasticity are required and process for producing the same.BACKGROUND ART[0002]With reference to gas turbine members, engine members for aircraft, chemical plant materials, engine members for automobile such as turbocharger rotors, and high temperature furnace materials etc., the strength is needed under a high temperature environment and an excellent oxidation resistance is sometimes required. For that reason, a Ni-base alloy and Co-base alloy have been used for such a high-temperature application. For example, as atypical heat-resistant material such as a turbine blade, a Ni-base superalloy which is strengthened by the formation of γ′ phase having an L12 structure: Ni3(Al,Ti) is listed. It is preferable that the γ′ phase is used to highly strengthen heat-resistant materials because it has an i...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C19/07C22F1/10
CPCC22F1/10C22C19/07
Inventor ISHIDA, KIYOHITOKAINUMA, RYOSUKEOIKAWA, KATUNARIOHNUMA, IKUOSATO, JUN
Owner JAPAN SCI & TECH CORP
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